2005-12-06 05:15:33

by Ananth N Mavinakayanahalli

Subject: [PATCH] kprobes: fix race in aggregate kprobe registration

From: Ananth N Mavinakayanahalli <[email protected]>

When registering multiple kprobes at the same address, we leave a small
window where the kprobe hlist will not contain a reference to the
registered kprobe, leading to potentially, a system crash if the
breakpoint is hit on another processor.

Patch below changes the order of hlist updation to make sure that there
is always a reference to the kprobe at the location.

Signed-off-by: Ananth N Mavinakayanahalli <[email protected]>
Acked-by: Prasanna S Panchamukhi <[email protected]>
Acked-by: Anil S Keshavamurthy <[email protected]>
---


kernel/kprobes.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.15-rc5/kernel/kprobes.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/kprobes.c
+++ linux-2.6.15-rc5/kernel/kprobes.c
@@ -400,9 +400,9 @@ static inline void add_aggr_kprobe(struc
list_add_rcu(&p->list, &ap->list);

INIT_HLIST_NODE(&ap->hlist);
- hlist_del_rcu(&p->hlist);
hlist_add_head_rcu(&ap->hlist,
&kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
+ hlist_del_rcu(&p->hlist);
}

/*

2005-12-06 21:18:39

by Keshavamurthy, Anil S

Subject: Re: [PATCH] kprobes: fix race in aggregate kprobe registration

On Tue, Dec 06, 2005 at 10:47:11AM +0530, Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli <[email protected]>
>
> When registering multiple kprobes at the same address, we leave a small
> window where the kprobe hlist will not contain a reference to the
> registered kprobe, leading to potentially, a system crash if the
> breakpoint is hit on another processor.
>
> Patch below changes the order of hlist updation to make sure that there
> is always a reference to the kprobe at the location.

Hi Ananth,
How do you like this patch? Here the old entry
will be replace with the new entry automically.

Signed-off-by: Anil S Keshavamurthy <[email protected]>

kernel/kprobes.c | 5 +----
1 files changed, 1 insertion(+), 4 deletions(-)

Index: linux-2.6.15-rc5-mm1/kernel/kprobes.c
===================================================================
--- linux-2.6.15-rc5-mm1.orig/kernel/kprobes.c
+++ linux-2.6.15-rc5-mm1/kernel/kprobes.c
@@ -399,10 +399,7 @@ static inline void add_aggr_kprobe(struc
INIT_LIST_HEAD(&ap->list);
list_add_rcu(&p->list, &ap->list);

- INIT_HLIST_NODE(&ap->hlist);
- hlist_del_rcu(&p->hlist);
- hlist_add_head_rcu(&ap->hlist,
- &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
+ hlist_replace_rcu(&p->hlist, &ap->hlist);
}

/*

2005-12-07 03:28:51

by Ananth N Mavinakayanahalli

Subject: Re: [PATCH] kprobes: fix race in aggregate kprobe registration

On Tue, Dec 06, 2005 at 01:18:24PM -0800, Keshavamurthy Anil S wrote:
> On Tue, Dec 06, 2005 at 10:47:11AM +0530, Ananth N Mavinakayanahalli wrote:
> > From: Ananth N Mavinakayanahalli <[email protected]>
> >
> > When registering multiple kprobes at the same address, we leave a small
> > window where the kprobe hlist will not contain a reference to the
> > registered kprobe, leading to potentially, a system crash if the
> > breakpoint is hit on another processor.
> >
> > Patch below changes the order of hlist updation to make sure that there
> > is always a reference to the kprobe at the location.
>
> Hi Ananth,
> How do you like this patch? Here the old entry
> will be replace with the new entry automically.

Your patch looks better.

Andrew,
Anil's patch depends on the list.h updates currently in -mm

> Signed-off-by: Anil S Keshavamurthy <[email protected]>
Acked-by: Ananth N Mavinakayanahalli <[email protected]>

>
> kernel/kprobes.c | 5 +----
> 1 files changed, 1 insertion(+), 4 deletions(-)
>
> Index: linux-2.6.15-rc5-mm1/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.15-rc5-mm1.orig/kernel/kprobes.c
> +++ linux-2.6.15-rc5-mm1/kernel/kprobes.c
> @@ -399,10 +399,7 @@ static inline void add_aggr_kprobe(struc
> INIT_LIST_HEAD(&ap->list);
> list_add_rcu(&p->list, &ap->list);
>
> - INIT_HLIST_NODE(&ap->hlist);
> - hlist_del_rcu(&p->hlist);
> - hlist_add_head_rcu(&ap->hlist,
> - &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
> + hlist_replace_rcu(&p->hlist, &ap->hlist);
> }
>
> /*

2005-12-07 09:55:10

by Andrew Morton

Subject: Re: [PATCH] kprobes: fix race in aggregate kprobe registration

Ananth N Mavinakayanahalli <[email protected]> wrote:
>
> > Hi Ananth,
> > How do you like this patch? Here the old entry
> > will be replace with the new entry automically.
>
> Your patch looks better.
>
> Andrew,
> Anil's patch depends on the list.h updates currently in -mm
>
> > Signed-off-by: Anil S Keshavamurthy <[email protected]>
> Acked-by: Ananth N Mavinakayanahalli <[email protected]>

Am feeling particularly uncreative. Please resend with a changelog.

2005-12-07 17:26:11

by Keshavamurthy, Anil S

Subject: [PATCH] kprobes: fix race in aggregate kprobe registration

When registering multiple kprobes at the same address, we leave a small
window where the kprobe hlist will not contain a reference to the
registered kprobe, leading to potentially, a system crash if the
breakpoint is hit on another processor.

Patch below now automically relpace the old kprobe with the new
kprobe from the hash list.

Signed-off-by: Anil S Keshavamurthy <[email protected]>
Acked-by: Ananth N Mavinakayanahalli <[email protected]>

kernel/kprobes.c | 5 +----
1 files changed, 1 insertion(+), 4 deletions(-)

Index: linux-2.6.15-rc5-mm1/kernel/kprobes.c
===================================================================
--- linux-2.6.15-rc5-mm1.orig/kernel/kprobes.c
+++ linux-2.6.15-rc5-mm1/kernel/kprobes.c
@@ -399,10 +399,7 @@ static inline void add_aggr_kprobe(struc
INIT_LIST_HEAD(&ap->list);
list_add_rcu(&p->list, &ap->list);

- INIT_HLIST_NODE(&ap->hlist);
- hlist_del_rcu(&p->hlist);
- hlist_add_head_rcu(&ap->hlist,
- &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
+ hlist_replace_rcu(&p->hlist, &ap->hlist);
}

/*